SERB JETS DOWNED BY NATO; ATTACKS BROADEN TO STRIKE ARMY, POLICE INSTALLATIONS.

Byline: Francis X. Clines and Steven Lee Myers The New York Times

As NATO forces stepped up their missile assault into the daylight hours, President Slobodan Milosevic of Yugoslavia maintained fierce resistance Friday both on the ground and in the air. Two of his MiG-29 fighters were shot down on what NATO claimed was a foray into neighboring Bosnia. The status of the pilots was unknown.

The sweep by Serb troops through the ethnic Albanian villages of Kosovo continued unabated, NATO said, despite the third straight day of air assaults that NATO officials claimed were succeeding and would remain unrelenting until Milosevic accepted peace.

Unconfirmed reports of violence against civilians continued as refugees from the ethnic Albanian majority of Kosovo, Serbia's southernmost province, straggled across the border to Macedonia with tales of increasing anarchy. There were also dramatic but unconfirmed reports of thousands of Kosovo refugees being pushed along a road with Serbian tanks at their backs.

In the airstrikes, a series of explosions rocked the outskirts of Belgrade on Friday night, with NATO officials saying the target list was being broadened specifically to include bunker positions of the Yugoslav military hierarchy in the Belgrade area as well as army and police outposts in Kosovo. NATO officials said even more severe assaults would follow.

President Clinton sought to appeal directly to the Serbian people in a televised statement, beamed by satellite throughout the region, in which he denounced Milosevic. ``He has diminished your country's standing, exposed you to violence and instability, and isolated you from the rest of Europe,'' Clinton declared in a broadcast translated into Serbo-Croat. ``Right now he's forcing your sons to keep fighting a senseless conflict that you did not ask for and that he could have prevented.'' It was unclear how widely the broadcast was viewed.

In Belgrade, the government has claimed ``minimal damage'' from the NATO attacks in reporting at least a dozen people killed and scores wounded. But Milosevic's U.N. representative, Vladislav Jovanovic, claimed ``hundreds of civilians'' had been killed in the airstrikes.

The downing of the two MiGs inside Bosnia by two U.S. F-15C fighters raised the question of whether Yugoslavia was attempting to extend the conflict and involve neighboring nations. Administration officials said the planes were shot down from a four-plane group that violated Bosnian air space. They crossed the western border of Serbia and were presumed to be heading aggressively toward NATO peace-keeping ground troops in Bosnia. The American interceptors were not from the NATO assault force but rather part of the Bosnia peace-keeping patrols.

The two losses, combined with earlier hits, means that by the Pentagon's count Milosevic has already lost a third of his premier air armada of 15 MiG-29s, highly rated Soviet fighter planes designed for both air-to-air and air-to-ground combat. In a subsequent incident, two MiG-21s crossed over Bosnia but retreated before they could be intercepted, NATO said.

``It was an act of desperation,'' State Department spokesman James Rubin said of the MiGs' incursion, characterizing it as evidence of Milosevic's frustration at the NATO assaults.

Milosevic warned

Earlier in the day, the Clinton administration issued a warning to Milosevic that any evidence of atrocities in Kosovo would be presented to war-crime investigators of the International Tribunal. The tribunal has opened an investigation focusing on Milosevic's role in the atrocity-ridden Balkan wars.

``The United States is extremely alarmed by reports of an escalating pattern of Serbian attacks on Kosovar Albanian civilians,'' Rubin said. ``We are using our national technical means to observe events in Kosovo and are prepared to share that information,'' he added, referring to satellite and aircraft surveillance photo records that could eventually be consulted in investigating specific allegations of atrocities.

One NATO official said intelligence agents as well were on the ground in Kosovo, trying to track Milosevic's troops as they routed and attacked ethnic Albanian villages.

``Of even more concern,'' said NATO's Supreme Commander Gen. Wesley Clark, ``are the so-called paramilitary forces, including gangs of hardened criminals which have in the past and are apparently now being employed in ethnic cleansing operations against the Kosovar Albanian population.''

The State Department said the growing violence was exemplified by such refugee reports - not yet confirmed independently - that Serb forces executed 20 ethnic Albanians in the village of Goden and were systematically targeting male civilians of fighting age.

Daylight strike

The third day of NATO's attack included the first daylight strike, although the brunt of the assault came at night as sirens once more braced the population of Belgrade, the Yugoslav capital. In midafternoon, an American cruiser, the USS Philippine Sea, fired two cruise missiles from the Adriatic. The missiles struck what officials described as ``a target of opportunity'' - military aircraft spotted at an air base - that had presented itself but was not part of the day's plan. Explosions rocked the southwestern edge of Belgrade shortly thereafter.

As dark fell over Yugoslavia, the main thrust of the attack began. Air-launched cruise missiles fired from B-52s based in England struck, followed by waves of fighters based in Italy, including F-117 stealth fighters.

For centuries, Kosovo has been a sacred province in Serb nationalist history, but 10 years ago, after Serbs slipped into the minority and ethnic Albanians became the overwhelming majority, Milosevic stripped the Kosovars of their autonomy. Last year, he opened an aggressive military campaign against them as they sought to regain self-rule. After agreeing under international pressure to a peace plan last fall, the authoritarian Serb leader resumed his ethnic cleansing attacks.

The reports of atrocities put more pressure on NATO to broaden its raids beyond air-defense and communications installations and focus on the Yugoslav forces than have been attacking the ethnic Albanians. Pentagon spokesman Kenneth Bacon said American and NATO forces were ``gradually focusing'' their strikes on army and police units in Kosovo.

In a telephone interview, Clark said the strikes were methodically following a plan that emphasized air defenses but also included strikes at the army and police headquarters. NATO released a list showing damage to army headquarters or barracks in Danilovgrad in Montenegro, Kursumilja in Serbia and Urosevac, Prizen and Pristina in Kosovo.

DEVELOPMENTS

NATO warplanes shoot down two Yugoslav MiG-29 jet fighters in neighboring Bosnia - a dramatic spillover of the conflict over Kosovo outside Yugoslavia's borders. Yugoslavia denies the NATO claim.

The third straight day of NATO airstrikes on Yugoslavia begins with the first daylight attack of the campaign, a cruise missile fired from a U.S. ship based in the Mediterranean Sea. Bombing and missile attacks resume late Friday.

Fighting continues throughout Kosovo, where more than 30 people are reported killed, according to the Kosovo Liberation Army's press agency. Thousands of ethnic Albanians are forced to march into a compound of a military factory in the central town of Srbica, according to the agency.

Protests against the airstrikes continue worldwide, and some NATO allies question the wisdom of further air raids. Italian Prime Minister Massimo D'Alema suggests a return to talks, and Greece also expresses reservations. But French, British, U.S. and other officials say NATO remains firmly united behind the attacks.

CAPTION(S):

Photo, Box

PHOTO Air raid sirens send two pedestrians running to shelter Friday in downtown Belgrade, Yugoslavia, as NATO airstrikes continued.

Associated Press 

BOX: DEVELOPMENTS (see text)